Air Injection Valve for a Muffler

ABSTRACT

An air injection valve includes: a valve housing having first and second housing halves coupled detachably to each other, the first housing half defining a first inner space and having a flat wall that is formed with a plurality of suction holes in fluid communication with the first inner space, the second housing half defining a second inner space and being formed with an outlet in fluid communication with the second inner space and adapted to be connected to the muffler; a valve seat secured in the second inner space and formed with a valve opening for permitting fluid communication between the first and second inner spaces; and a flexible thin film reed having one end secured to the valve seat for covering and uncovering the valve opening.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an air injection valve for a muffler, more particularly to an air injection valve formed with a plurality of holes for suction of fresh air into a muffler.

2. Description of the Related Art

FIG. 1 illustrates a secondary air injection (SAI) device for a motorcycle. The SAI device provides a function of injecting intermittently fresh air into a muffler (not shown) for assisting catalytic conversion of hydrocarbon and carbon monoxide in an exhaust gas stream from an engine (not shown) into water and carbon dioxide. The SAI device includes: a housing 10 defining an air inlet 11, a gas outlet 12 adapted to be connected to the muffler (not shown), a thin L-shaped tube 13 adapted to be connected to the carburetor, a control mechanism 14 mounted in the housing 10 and cooperating with the L-shaped tube 13 for controlling the air stream into the carburetor, and a vibrating reed valve 15 for controlling injection of the fresh air into the muffler.

The aforesaid conventional SAI device is disadvantageous in that it has a relatively large size and that it generates noise when fresh air is intermittently injected into the housing 10 through the air inlet 11 during operation of the engine.

SUMMARY OF THE INVENTION

Therefore, the object of the present invention is to provide an air injection valve that can overcome the aforesaid drawbacks of the prior art.

According to this invention, there is provided an air injection valve for a muffler. The air injection valve comprises: a valve housing having first and second housing halves coupled detachably to each other, the first housing half defining a first inner space and having a flat wall that is formed with a plurality of suction holes in fluid communication with the first inner space, the second housing half defining a second inner space and being formed with an outlet in fluid communication with the second inner space and adapted to be connected to the muffler; a valve seat secured in the second inner space and formed with a valve opening for permitting fluid communication between the first and second inner spaces; and a flexible thin film reed having one end secured to the valve seat for covering and uncovering the valve opening.

BRIEF DESCRIPTION OF THE DRAWING

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of this invention, with reference to the accompanying drawings, in which:

FIG. 1 is a sectional view of a conventional secondary air injection device;

FIG. 2 is a front perspective view of the preferred embodiment of an air injection valve according to this invention;

FIG. 3 is an exploded perspective view of the preferred embodiment;

FIG. 4 is a perspective view of an assembly of a first housing half, a filter and a positioning member of the preferred embodiment;

FIG. 5 is a rear perspective view of the preferred embodiment;

FIG. 6 is a front schematic view of a valve seat of the preferred embodiment;

FIG. 7 is a rear perspective view of the valve seat of the preferred embodiment;

FIG. 8 is a schematic side view to illustrate a state where a valve opening in the valve seat is covered by a thin film reed of the preferred embodiment;

FIG. 9 is a schematic side view to illustrate another state where the valve opening in the valve seat is uncovered by the thin film reed of the preferred embodiment; and

FIG. 10 is a schematic view of a muffler provided with the air injection valve of the preferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 2 to 4 illustrate the preferred embodiment of an air injection valve 200 according to this invention for mounting to a muffler 300 (see FIG. 10).

The air injection valve 200 includes: a valve housing 2 having first and second housing halves 21, 22 coupled detachably to each other, the first housing half 21 defining a first inner space 210 (see FIG. 4) and having a flat wall 211 that is formed with a plurality of suction holes 212 in fluid communication with the first inner space 210, the second housing half 22 defining a second inner space 220 and being formed with an outlet 221 in fluid communication with the second inner space 220 and adapted to be connected to the muffler 300; a valve seat 23 secured in the second inner space 220 and formed with a valve opening 230 for permitting fluid communication between the first and second inner spaces 210, 220; a flexible thin film reed 24 (see FIGS. 6 to 8) having one end secured to the valve seat 23 for covering and uncovering the valve opening 230; a filter 25 mounted detachably in the first inner space 210 and covering the suction holes 212; and a positioning member 26 that is in the form of a perforated and corrugated thin plate fitted securely into the first inner space 210 so as to position the filter 25. The suction holes 212 in the first housing half 21 are arranged in an array that has a size conforming to that of the valve opening 230 in the valve seat 23.

In this embodiment, a curved stopper 27 (see FIGS. 7 to 9) having one end secured to the valve seat 23 and a shape conforming to that of the thin film reed 24 so as to stop further flexing of the thin film reed 24 when the thin film reed 24 is flexed to uncover the valve opening 230 due to a negative or sub-atmospheric pressure produced in the muffler 300.

Referring now to FIG. 5, in combination with FIG. 3, the second housing half 22 has a flat wall 223 that is opposite to the flat wall 211 of the first housing half 21 in a first direction, and an end flange 224 that extends from one end of the flat wall 223 of the second housing half 22, that is disposed transversely of the flat wall 223 of the second housing half 22, and that is adapted to be connected and fastened to a muffler housing 3 (see FIG. 10) of the muffler 300 through screw means. The suction holes 212 in the flat wall 211 of the first housing half 21 are aligned with the valve opening 230 in the valve seat 23 in the first direction. The outlet 221 in the second housing half 22 extends through the end flange 224 and faces in a second direction transverse to the first direction.

Referring to FIG. 10, the muffler 300 includes a muffler housing 3 defining a chamber 30 therein, an exhaust gas inlet 31, an exhaust gas outlet 32, and an air inlet 33. The muffler housing 3 is provided with an end flange to be connected to the end flange 224 of the second housing half 22 of the air injection valve 200. The air inlet 33 of the muffler housing 3 extends through the end flange on the muffler housing 3 and is in fluid communication with the chamber 30 of the muffler housing 3. A catalyst 4 is mounted in the chamber 30 and is disposed between the exhaust gas inlet 31 and the exhaust gas outlet 32.

In operation, due to repeated suction and compression strokes of the engine, pulsating of air pressure in the chamber 30 of the muffler housing 3 occurs, which results in intermittent injection of fresh air into the chamber 30 in the muffler housing 3 through the suction holes 212 in the first housing half 21 of the air injection valve 200 and the air inlet 33 of the muffler housing 3. During a compression stroke, the exhaust gas discharged from the engine enters into the muffler housing 3 through the exhaust gas inlet 31, passes through the catalyst 4 so as to be treated to reduce the amount of the hydrocarbon and carbon monoxide thereof, and is discharged through the exhaust gas outlet 32. At this stage, the pressure in the muffler housing 3 is changed into a positive condition, i.e., greater than the atmospheric pressure, due to receipt of the exhaust gas therein, which results in a positive pressure in the second inner space 220 in the second housing half 22 of the air injection valve 200, which, in turn, results in covering of the valve opening 230 by the thin film reed 24. During the suction stroke, the gas in the muffler housing 3 is withdrawn into the exhaust gas system, which results in a negative pressure in the muffler housing 3 and in the second inner space 220 in the second housing half 22 of the air injection valve 200. At this stage, the thin film reed 24 is flexed due to a positive pressure difference between the atmospheric pressure and the pressure in the muffler housing 3, thereby opening the valve opening 230 and permitting fresh air to enter into the muffler housing 3 to mix with the exhaust gas so as to assist catalytic conversion of the hydrocarbon and carbon monoxide into water and carbon dioxide.

The intermittent injection of fresh air into the second inner space 220 in the second housing half 22 of the air injection valve 2 during operation of the engine can cause generation of noise. However, by forming the suction holes 212 in the flat wall 211 of the first housing half 21 of the air injection valve 2, the noise can be considerably reduced. In addition, not only can the filter 25 serve to prevent dust and water from entering into the air injection valve 200, it can also provide a further reduction in the noise. Moreover, the size of the air injection valve 200 is considerably reduced as compared to the aforesaid conventional SAI device.

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation and equivalent arrangements. 

1. An air injection valve for a muffler, comprising: a valve housing having first and second housing halves coupled detachably to each other, said first housing half defining a first inner space and having a flat wall that is formed with a plurality of suction holes in fluid communication with said first inner space, said second housing half defining a second inner space and being formed with an outlet in fluid communication with said second inner space and adapted to be connected to the muffler; a valve seat secured in said second inner space and formed with a valve opening for permitting fluid communication between said first and second inner spaces; and a flexible thin film reed having one end secured to said valve seat for covering and uncovering said valve opening.
 2. The air injection valve of claim 1, further comprising a filter mounted detachably in said first inner space and covering said suction holes.
 3. The air injection valve of claim 2, further comprising a positioning member that is in the form of a perforated thin plate fitted securely into said first inner space so as to position said filter.
 4. The air injection valve of claim 3, wherein said perforated thin plate is corrugated.
 5. The air injection valve of claim 1, further comprising a curved stopper having one end secured to said valve seat and a shape conforming to that of said thin film reed so as to stop further flexing of said thin film reed when said thin film reed is flexed to uncover said valve opening.
 6. The air injection valve of claim 1, wherein said second housing half has a flat wall that is opposite to said flat wall of said first housing half in a first direction, and an end flange that extends from one end of said flat wall of said second housing half, that is disposed transversely of said flat wall of said second housing half, and that is adapted to be connected to the muffler, said suction holes being aligned with said valve opening in said first direction, said outlet extending through said end flange and facing in a second direction transverse to said first direction.
 7. The air injection valve of claim 6, wherein said suction holes are arranged in an array that has a size conforming to that of said valve opening.
 8. A muffler comprising: a muffler housing defining a chamber therein, an exhaust gas inlet, and an exhaust gas outlet; a catalyst mounted in said chamber and disposed between said exhaust gas inlet and said exhaust gas outlet; and an air injection valve mounted on said muffler housing and including a valve housing having first and second housing halves coupled detachably to each other, said first housing half defining a first inner space and having a flat wall that is formed with a plurality of suction holes in fluid communication with said first inner space, said second housing half defining a second inner space and being formed with an outlet in fluid communication with said second inner space and said chamber, a valve seat secured in said second inner space and formed with a valve opening for permitting fluid communication between said first and second inner spaces, and a flexible thin film reed having one end secured to said valve seat for covering and uncovering said valve opening.
 9. The muffler of claim 8, wherein said air injection valve further includes a filter mounted detachably in said first inner space and covering said suction holes.
 10. The muffler of claim 9, wherein said air injection valve further includes a perforated thin plate fitted securely into said first inner space so as to position said filter.
 11. The muffler of claim 8, wherein said air injection valve further includes a curved stopper having one end secured to said valve seat and a shape conforming to that of said thin film reed so as to stop further flexing of said thin film reed when said thin film reed is flexed to uncover said valve opening.
 12. The muffler of claim 8, wherein said second housing half has a flat wall that is opposite to said flat wall of said first housing half in a first direction, and an end flange that extends from one end of said flat wall of said second housing half, that is disposed transversely of said flat wall of said second housing half, and that is connected to said muffler housing, said suction holes being aligned with said valve opening in said first direction, said outlet extending through said end flange and facing in a second direction transverse to said first direction.
 13. The muffler of claim 12, wherein said suction holes are arranged in an array that has a size conforming to that of said valve opening. 